There’s one key takeaway from last week’s IPCC report

(The Guardian, 15 Oct 2018) Cut carbon pollution as much as possible, as fast as possible.

The Paris climate agreement set a target of no more than 2°C global warming above pre-industrial temperatures, but also an aspirational target of no more than 1.5°C. That’s because many participating countries – especially island nations particularly vulnerable to sea level rise – felt that even 2°C global warming is too dangerous. But there hadn’t been a lot of research into the climate impacts at 1.5°C vs. 2°C, and so the UN asked the IPCC to publish a special report summarizing what it would take to achieve the 1.5°C limit and what the consequences would be of missing it.

The details in the report are worth understanding, but there’s one simple critical takeaway point: we need to cut carbon pollution as much as possible, as fast as possible.

We’re about to burn through the 1.5°C carbon budget

Depending on how we define ‘pre-industrial temperatures’ and how fast we keep consuming fossil fuels, we’ll likely burn through the rest of the 1.5°C carbon budget within the next 3 to 10 years. To stay below 1.5°C, the IPCC therefore concludes the world must embark on a World War II-level effort to transition away from fossil fuels, and also start removing carbon dioxide from the atmosphere at large scales – anywhere from 400bn to 1.6tn tons of it.

Realistically, this isn’t going to happen. We’re currently on track for more than 3°C global warming by 2100. We can do better than that if countries ratchet down their carbon pledges and implement more aggressive climate policies, but with some nations moving in the wrong direction, like the US and potentially Brazil electing climate denier presidents, even staying below 2°C is looking increasingly less likely.

However, these are somewhat arbitrary targets. 1.5°C is less dangerous than 2°C, which is less dangerous than 2.5°C, which is less dangerous than 3°C, and so on. Any further warming from today’s already-hot temperatures (1°C warmer than pre-industrial) increases global risks, and staying below any of these temperature thresholds is going to require aggressive climate policies from countries around the world.

The answer to the question “what should aim for?” is simple: cut carbon pollution as much as possible, as fast as possible. Until the world reaches zero carbon, the answer will always be the same.